Biological wastewater treatment is the process of removing organic and biological contaminants from wastewater via biological processes. Its objective is to produce an environmentally safe fluid waste stream suitable for disposal or reuse.
Biological wastewater treatment may be aerobic (which take place in the presence of oxygen) or anaerobic (which occur in the absence of oxygen). In both processes, a portion of biological contaminants in water (e.g. sugars, fats, organic short-chain carbon molecules, etc.) is digested by bacteria and broken down into simpler components, while another portion is bound into floc.
U.S. Pat. No. 7,081,203, which is incorporated herein by reference and was invented by the inventor of the present invention, discloses a compact, ground surface mounted wastewater treatment unit module. The module is surface mounted on a selected substrate such as a scarified native soil. A watertight receiving basin is located on the substrate. The basin is at least partially filled with a lower layer of packing media, suitable for support of biological growth, and then with at least a first and a final layer of a porous granular media. A standpipe introduces wastewater to be treated, and such wastewater is distributed to the packing at the lower reaches of the basin. The wastewater flows up through the packing, and into the first layer of a porous granular media, and thence upwardly and outwardly via capillary action and molecular attraction, and ultimately though the final porous granular media. Treated wastewater is either collected or absorbed in an absorption foot interface between the final medium and the native earth below.